Human Evolution On Trial By Terry Toohill

These pages comprise the efforts of Terry Toohill to explain our human origins through the perspective of evolution. Each post deals with specific aspects of the factors that have influenced not only our own evolution, but those that have driven the evolution of all life on planet earth, from its humble origins, billions of years ago.

Saturday, 20 June 2009

Following private correspondence with author Terry Toohill, I've agreed to serialise his book “Human Evolution On Trial – A Case For The Defence" here at Remote Central, in the hope that not only will readers be interested to read what he has to say, but will also be prompted to add comments of their own, on what is a suitably detailed and well-researched set of chapters charting the author's take on what he also refers to as “From Apes Until today – A Case In Defence Of Human Evolution”.

I have been advised by Terry that the text is subject to copyright, as it has been placed in the Alexander Turnbull Library of New Zealand, and although I don't have details at the moment, copies may be available for purchase from the author. But for the time being, it's free to read here, so I hope readers find this a worthwhile and thought-provoking book, further instalments of which are scheduled to appear on this blog over the coming weeks.

I should also add as the usual disclaimer that the views and opinions contained therein are solely those of the author, and that he alone is responsible for the text and the details it contains, as he is the sole author - I hope that covers it.

So without further ado, here's an introduction from Terry Toohill, and my thanks to him for allowing his work to be published here at remote central.

"This extract is from partway through an account I have compiled on our evolution. My basic theme is that our cultural beliefs always influence how we interpret all phenomena. Because Judeo-Christian beliefs have been with us so long they have fundamentally influenced how we view the world. This has hampered an understanding of our origin as a species. I show that when we eliminate a biblical perspective any problems in our complete understanding of evolution disappear. On the other hand once we understand our evolution we easily see the history that lies behind stories in the Old Testament. I have divided the account into five parts.

In Part I, “Beginning - The Present”, I explain how genes work. I show how, in practice, populations or whole species can be simply regarded as a collection of genes in various proportions. I point out we could even say that each individual gene travels through a population on its own independent wave.

In Part II“Migration – The Past” I use what we know of New Zealand’s history and prehistory to show how recent human evolution provides evidence in support of the idea.

In Part III, “Biological Rules - Knowledge” I start with the short summary of the history of the earth presented here. I next look at the development of geology and then the complex question of what is a species. I show that any definition we attempt is inadequate. I then return to how biological evolution works.

Part IV“Wandering – Becoming Human” starts with our ape ancestors. I then look at the progressive development of Stone Age technology. I show that in some ways we can regard technology as evolving in a similar way to organic evolution; diversification, then hybridising followed by selection. Remaining chapters in this part follow and explain our ancestors’ biological development through various named species from Homo erectus to Neanderthals and modern humans. I argue that the ready acceptance of a mtEve single ancestor derives primarily from the influence of our Judeo-Christian background.

In Part V, I simply follow the course of modern human evolution until written records are able to tell us the historical situation in each region. I show all our culture, our knowledge, our beliefs and our skills are the result of a similar mixing, or “interbreeding”, followed by selection or culling. As a last point I compare human migration through islands in the Mediterranean Sea to that through islands in the Pacific Ocean. Finally I use my ideas to explain many stories in the Old Testament.

Preface - A Brief History of the World

Time

History needs dates and so I had better first provide a framework for all the evidence. To understand the lengths of time involved for various events during the earth’s history try this summary. It is an exponential time scale. There is a condensed version in the form of a chart starting a few pages ahead and I’m sure you’ll find it useful to refer to it when necessary. But first of all I’ll explain it.

The most recent events are at the top, or beginning of the chart, as they are in geological strata or layers. The older, or lower, layers are compressed, also as they are in geological strata. To read it in the order things happened you have to start at the bottom, or far end of the chart, but you can start anywhere. As you move back in time, or down the list, each division covers the same length of time as everything before it (or above it). As you move up the column towards the present each division halves the time between then and today. The chart has the advantage of being close to how we actually view time because as Gohau (1991) writes “every history favors the present over the past, if only because of the unequal amount of data available for the two”. I have juggled the figures a little in places to produce more significant dates but it still basically doubles all the way.

To make it relevant for humans I’ll start with a human generation of twenty-five years and keep doubling the time.

For convenience we’ll begin at 2000 AD. Twenty-five years takes us back to 1975. Fifty years ago it was 1950, soon after the end of the Second World War. Double it again and we are back 100 years, the beginning of the twentieth century, and so on.

Doubled again takes us back to 1800 AD when we each have over two hundred and fifty ancestors in our individual pedigrees. The steam engine had just come into general use (Fyrth and Goldsmith 1965) and so we could use this date to mark the beginning of the Industrial Revolution and the beginning of geology.

Double again to four hundred years ago and we are about the time of the death of Queen Elizabeth I of England (March 1603). We are well into the time of European exploration, exploitation and expansion around the world and the beginning of the latest round of extinctions. We are nearing the time of a million ancestors each. The invention of both the telescope and the microscope around this time meant science could begin. Both Lucilio Vanini and Giordano Bruno were burnt at the stake for their beliefs. Archbishop Ussher calculated the earth had been created in 4004 BC, near enough to 6400 years ago.

Eight hundred years takes us back to just 1200 AD though. There is no doubt Maori had become well established in New Zealand by this time. The Crusades were well under way and Genghis Khan took control of the Mongols.

Sixteen hundred years ago marks the withdrawal of the Roman Empire from much of Western Europe, although an argument can be made that “The West” is a continuation of it. The Anglo-Saxon movement into England coincided with the temporary disruption of the Roman Empire in Britain. Human expansion beyond Samoa into Eastern Polynesia was well underway.

Double 1600 years to 3200 years ago (1200 BC) and people using Lapita pottery were about to reach Tonga and Samoa. We are also at about the time of Ramesses III of Egypt and the migration of the Sea People through the Mediterranean Islands, what we might call the last point of the human star. It may also be the time of any kingdom of Israel in the Middle East under David and Solomon although not all people regard all these events as being contemporary.

Double again to 6400 years ago (4400 BC) and we are at about the beginning of cities in the Tigris and Euphrates River valleys (Mesopotamia) in what is now Iraq. Much older towns have been found just outside the region though (for example at Jericho). The keeping of records through the use of writing probably began around this time. And Archbishop Ussher believed the earth had been created then. People in the Balkans were working copper (James 1991) and the Austronesian-speaking people began their expansion from Taiwan. People with the Linear Pottery or Danubian culture were moving into Europe.

If we double again we reach 12,800 years ago but we’ll round the date to 12,500. We are near the end of the ice age and the beginning of human movement into the extreme end of the Northwest European point of the human star and into the American sub-point. The first steps towards farming were probably also made at this time both in the Middle East (the Fertile Crescent) and in Southeast Asia (the Hoabinhian culture).

Double the time again and we have 25,000 years ago, about the time people with the “Gravettian” stone-age culture moved into Western Europe from east of the Carpathian Mountains, from Southern Russia. Modern humans finally replaced the Neanderthals, probably at least partly through the formation of hybrids. The Gravettian people probably used the same route as the Corded Ware people were to take 18,000 years later. African and European cattle separated at about this time.

About 50,000 years ago humans known as Cro-Magnon started moving into Europe, most likely from the southeast via Turkey and Greece. They introduced the “Aurignacian” technology. At the opposite side of the human star people were able to move into Australia for the first time.

Fully modern humans, or Homo sapiens, are said to have left Africa by the time we double again to 100,000 years ago. They may have been held up in the Middle East because Neanderthals (Homo neanderthalensis) keep popping up there over the next 50,000 years.

200,000 years ago we have Homo heidelbergensis in Europe (the first fossils of it were found near Heidelberg). Neanderthals and modern humans both presumably developed from this species (possibly with some input from earlier Homo erectus). Neanderthals’ culture is called “Mousterian” and involved the “Levallois” technique of working stone.

The Levallois developed some time between 200,000 and 400,000 thousand years ago and 400,000 years ago is about when Homo heidelbergensis developed, presumably from some sort of Homo erectus.

By 800,000 years ago the species Homo erectus had probably reached the geographical extremes of their range. It was not until four divisions more recently that humans were able to expand further, into Australia. We’ll return to this summary in a while but now is a convenient place for us to have a rest and for me to show you the chart.

A short history of the Earth.

0: 2000 AD The New Millennium

25: One generation, back to 1975. I left the Manawatu and returned to Northland

50: End of Second World War (roughly). I was born (a little less roughly)

100: Beginning of the twentieth century. Humans found they could fly after all

200: The Industrial Revolution began and Europeans started moving into Australia and New Zealand

400: Time of Queen Elizabeth I. Europeans off learning about the world. Bruno executed

800: Maori in New Zealand by this time. Inquisition established

1600: Decline of Roman Empire, Anglo-Saxons into England

3200: About the time of Rameses III of Egypt and the Kingdom of Israel. Lapita pottery people to Tonga and Samoa.

6400: Cities developing in the Middle East and possibly Egypt. Linear pottery-bearing and Austronesian-speaking people begin their expansion.

12,500: End of ice age. Beginning of farming and Hoabinhian culture. Humans able to enter what I call the American subpoint of the human star

25,000: In Europe the Gravettian stone tool culture moved in from the northeast

50,000: Aurignacian stone tool culture into Europe from the southeast. (Cro-Magnon man). First humans into Australia

100,000: Human expansion out of Africa. They and Neanderthals alternate in the Middle East for half the time between today and then

1.875 million: Evolution of Homo erectus in Africa and Asia. Ice ages well established

3.75 million: Good fossil evidence for Australopithecus (Lucy)

7.5 million: Roughly time of split between humans, chimps and gorillas. Three-toed horses out of America

15 million: Africa became jammed into Asia and Europe. Ancestors of modern apes able to move between these continents

30 million: Mid-Oligocene geological epoch. Apes separated from monkeys during this period

65 million: End of the Cretaceous geological period and the dinosaurs. Continents started splitting and age of mammals began. Monkeys already developing

130 million: Beginning of Cretaceous (end of the Jurassic period). The Cretaceous fills half the time between today and then

260 million: Beginning of the Permian geological period. Most of the oldest rocks in New Zealand were laid down over the period from the Permian to the end of the Jurassic. Again this took up half the time between today and then

520 million: End of the Cambrian geological period. The first mass extinctions we are aware of

1040 million: Possibly an ice age

2080 million: Primitive life on Earth

4160 million: Round about the beginning of the Earth

Now to carry on:

Double again to 1.6 million years ago and we have Homo erectus beginning their expansion. We should probably call them the first humans. The latest series of ice ages had started a little before this time. There have been up to twenty cycles of extreme cold followed by periods as warm as or warmer than today. The climate had actually already been steadily cooling for more than 30 million years before this though. The period of the ice ages is known as the “Pleistocene geological epoch”. The beginning of the Pleistocene, about two million years ago, also marks the end of the Tertiary and the beginning of the Quaternary geological period.

Homo erectus evolved more than 1.7 million years ago but I’ll use 1.875 million years. When that is doubled it comes up 3.75 million years ago. From about this date there is good fossil evidence in Africa for presumed Homo erectus and human ancestors in the form of “Lucy” and other Australopithecus species (Johanson and Edey 1982). Some genetic evidence has been interpreted as showing humans, chimpanzees and gorillas may have finally separated as recently as this date (Gribbin and Cherfas 2001). Various species of Equus and camels moved out of North America also about this time.

Doubled again is 7.5 million years and three-toed horses moved out of North America. This is also about the earliest time given for the split between chimpanzees and humans, although gorillas may have separated even earlier. A fossil of this age that could well lie on the line to humans has recently been found in Chad (Lemonick and Dorfman 2002).

Fifteen million years ago, in the middle of the Miocene geological epoch, Africa became jammed up against Asia and Europe (Attenborough 1987). This allowed the ancestors of the modern (or brachiating) apes to move between Africa and Asia (brachiating is the ability to swing or hang from branches by your arms). In fact it is possible the ancestors of the present African apes (including humans) actually moved into Africa from Asia (Gribbin and Cherfas 2001). The gibbons may have separated from the rest of the ape line as early as fifteen million years ago. They have become particularly effective brachiators. The orangutan separated eight to ten million years ago.

Double again and we are in the middle of the Oligocene geological epoch, at 30 million years ago. Three-toed horses appeared in North America and the ancestors of deer and giraffes separated from other ruminants during this period. Camels and llamas had already parted from them. We can use evidence from these and many other species to prove what a friend has called the wave theory of genetic, cultural and technological evolution. This theory is able to help us interpret the evidence for our evolution from apes until today. So do we need to go further back if we are concerned just with this? But I’m on a roll and for now I’ll just keep doubling the time until I reach the beginning of the earth.

Apes seem to have separated from monkeys during this period. Apes diverged into many species most of which (apart from some of the later brachiating ones) eventually became extinct. During the Oligocene the continents were at their lowest altitude, having been eroded down since well back in the Cretaceous period. The climate was very warm and seas were at their highest. From the Oligocene until the present the continents start bumping into each other again. Mountains rise and the sea is able to sink into deeper ocean basins. This period also marks the beginning of the climate cooling that led ultimately to the latest series of ice ages. The immediate cause of the cooling was probably the opening of the gap between Australia and Antarctica. This allowed the southern circum-polar current to develop (Stevens 1985).

Double again and we have 60 million years but we’ll make it 65 million years, which marks the end of the Cretaceous geological period and the beginning of the Tertiary geological period. It also marks the extinction of the dinosaurs and beginning of the age of mammals. Some people believe the dinosaurs didn’t actually become extinct. Small versions that had evolved feathers, probably to keep warm, evolved into birds.

The Cretaceous itself in fact lasted about 65 million years and so the Cretaceous began 130 million years ago. This earlier date marks the end of the Jurassic period and the beginning of another breakup of continents. Virtually all the sea floor on earth is younger than this date and most of it is younger than half this age (Jones 2000). The lowering of mountain ranges by erosion and the gradual filling of sea floor with the sediment during the sixty-five million years of the Cretaceous eventually had the effect of raising sea levels and partially flooding the continents. The gradual isolation and size reduction of the continents during the Cretaceous period and consequent climate and environmental change may have had as much to do with the eventual extinction of the dinosaurs outside North America as did the asteroid collision. Dinosaur extinction was actually very protracted; at least hundreds of thousands of years (Jones 2000). And possibly millions but humans like the idea of catastrophes. In fact many people hope the world is going to end soon.

The massive eruption of volcanoes on the Deccan plateau of India near the end of the Cretaceous would have contributed to the dinosaur extinction and could be partly responsible for the layer of heavy metals found in sediments from 65 million years ago throughout the world. Although Richard Corfield (2001) does mention this possibility he seems to suggest the idea has been rejected largely because of political and funding considerations. He actually offers no evidence to dispute it. Most mass extinctions have coincided with large volcanic eruptions though (Wade 2001).

The ancestors of monkeys and lemurs had separated from other mammals at some time during the Cretaceous, probably along with the development of flowering plants, especially trees (Tudge 1996). Flowering plants appeared in the mid-Cretaceous and the evolution of grass may have been the final straw, so to speak, for the dinosaurs. Grasses didn’t actually reach their major expansion until more recently though (at the beginning of the Miocene epoch about 25 million years ago) and ruminants or cud-chewing animals seem to have started developing a little before that time. The expansion of grassland was also responsible for the development of horses.

Double the time again and we get 260 million, the beginning of the Permian period. The Permian is actually in the Paleozoic geological era but the Paleozoic ends with the end of the Permian, about 235 million years ago. Great volcanic eruptions and a series of ice ages similar to the ones the earth has just been through mark the end of the Permian. But the continents were in much different positions than they are today. The time also marks easily the greatest mass extinction event we are aware of. It makes the extinction event at the end of the Cretaceous (which included the extinction of the dinosaurs) look relatively minor, about number five on a list of severity.

Double again: 520 million is the end of the Cambrian period, marked by the extinction of much of the variety of life that had developed by that time. The Cambrian began about 570 million years ago with a huge explosion of life forms (Corfield 2001). Supporters of the Intelligent Design theory of evolution apparently believe this happened through a creation (Wells 2000 and Dembski and Kushiner 2001). Anyway whether it happened by creation or not is irrelevant to whether or not we evolved from apes.

1040 million years is in the Precambrian era and someone else can look for significance in that date but some evidence suggests complex life began about then (Wade 2001). Intelligent Design supporters presumably would say through another creation event. Until James Hutton’s time most geologists used the idea there have been several “creations” to explain the fact that throughout the world rocks of the same age have similar collections of fossils, many of them not present in more recent levels (Gohau 1991). Most early geologists believed each group of earlier life had been destroyed by catastrophes. There had been a series of beginnings. Others began to see a basic thread that indicated life had changed or evolved through the history of the earth.

We can see that the same old argument carries on in the conflict between creationists and evolutionists. The term creationist covers a huge variety of beliefs though. Some of them even accept evolution has occurred but that it has happened by design (Wells 2000 and Dembski and Kushiner 2001).

The preference of any individual to accept either gradual or sudden change (or even no change at all) as an explanation for the development of life on earth depends very much on what has been, or is, important in their own life. It is difficult for us to imagine the world has ever changed more than it has over our own lifetime. We also carry many mythconceptions from our childhood. I believe the conflict between a belief in gradual or sudden change is actually at the core of the debate between the “spread origin” and “single origin” theories of human evolution. You will be able to decide for yourself which is the most likely theory as we examine the evidence.

2080 million years may be significant (perhaps the beginning of life itself) and the earth is said to have begun a little more than 4160 million years ago."

This contents list will help anybody interested understand the thread of logic that runs through this case. Not all chapters are up yet but I don't think there's any hurry. I'm more than happy to argue with anyone who wishes to. And, of course, I'm more than happy to hear from you if you're able to improve the defence case, or even just agree with it.

I need first of all to explain how I have set out the evidence I have gathered [Order], and why. Next we’ll look at some debates over how evolution happens, or, according to some people doesn’t happen at all [The Prosecution]. I’ll then introduce myself to you and examine how we come to know what we think we know.

Our individual conception of the universe evolves through the input of conceptions we are exposed to as we grow up. New ideas always trickle gradually to various groups of individuals though. In the early 1600s Galileo completely upset our collective conception. He proved the earth moves around the sun. But a survey in France nearly four hundred years later showed that one third of the people there still believed the sun moves around the earth (Gohau 1991). Presumably some still believed the earth is flat.

In spite of the huge advances in the explanation of human origin made over the last 150 years a huge number of different theories still circulate about how we humans have arrived on earth. Most of these theories involve distorting, or selectively ignoring (perhaps unconsciously), relevant evidence. Many fossils have been discovered and forensic science has helped immensely in examining and interpreting all this evidence. A great deal of work has also been done on the ways genes work and how they, technology, culture and languages move, and change, through time and space. But in many parts of the world there has recently been an increase in religious extremism and growing unwillingness to accept the idea that we humans are basically a kind of ape.

Perhaps the one idea we can assume is true is that debate always improves our own ideas. The process produces a sort of hybrid vigour. Any opposition also clarifies our own ideas and theories. It focuses our point of view. To provide a framework for my explanation of the evidence I have decided to present this story as an argument against the evolution-deniers among us. I will use the idea that a defendant, Human Evolution, is on trial. Of course this trial is really about much more than just that. For example, cultural beliefs have always been used to justify both economic exploitation and the acts of terrorism committed in response. The trial is really about the attitude we have to our surroundings and the way we treat our planet and its inhabitants.

As we wind our way through the evidence I will imagine you, the reader, to be a member of the jury. But at various times you will probably consider yourself to be either a member of the defence or part of the prosecution. The defence case will explain exactly how, in the right circumstances, collections of genes and even individual genes spread through populations or into new regions. One of my friends has called this the wave theory of genetic, cultural and technological evolution. The jury will see that this theory totally explains our evolution from the apes until today. In fact it explains the evolution of all species at all times. Along with many other things. Even our collective and individual ideas and beliefs evolve in much the same way. I’ll begin the defence case once I’ve completed this introductory chapter. Much later, when I have explained exactly how the wave theory works, it will be sensible for us to follow our more recent history from this perspective.

The members of the prosecution are those in society who, for various reasons, claim the main outline of our evolution is not proven beyond reasonable doubt. At this point I would point out to the jury that members of the prosecution cannot actually offer any evidence, apart from ancient beliefs, to support a detailed, and certainly not a unified, alternative explanation for how, when, where and why we arrived on earth. Luckily we have a right as citizens in a democracy to question everybody’s motives. Although not all members of the prosecution belong to powerful or influential elements in society many of them do. Perhaps economics comes into it. Perhaps they hope their God is going to come back soon and, like their parents used to do, clean up any mess they make.

Order

Unfortunately I haven’t always found it possible to present all the evidence that supports a particular conclusion in its logical place. For example evidence that explains the human migration “North to Alaska” and then into the Americas also supports many conclusions I offer long before we reach that point. However for various reasons it is most convenient to present the particular evidence towards the end of my story. I’m sure the jury will still follow the various threads and not find this to be a problem though.

I admit that some items of the evidence may be subject to several interpretations. But surely the jury will be aware of the fact that it is usually possible to prove anything by selectively ignoring some, or even a great deal, of relevant evidence. Politicians and other powerful and influential people use the technique expertly. It’s usually successful. We cannot all know all the evidence. Although I realise many members of the jury will already know a great deal of the information presented, I’m sure you will all enjoy having it gathered together in one place and at your fingertips. Others of you will know less about the subject and I hope you find it as fascinating as we members of the defence do. Besides there is a difference between blindly accepting that we evolved from apes, and having the knowledge of how it happened. And it helps us understand events today.

The evidence I invite the jury to consider will concern the past. You might be tempted to say our ancient past is not important. But I would like to point out that our conception of the past and our beliefs about it influence our actions in the present. And of course these actions, in turn, will influence our future. I would suggest, though, in order to understand the past, let alone the future, we need first to understand the present.

In Part I - “Beginning” I will therefore first of all examine what we know about you, the individual person, and I explain how genes work. I then expand the view to include your progressively more distant relations, neighbours and friends. Even to the distribution of different human types around the earth today (“The Human Star”[A Map]). Although the defendant is Human Evolution along the way I will call on evidence from other creatures, and even from plants, to explain various aspects.

In Part II - “Migration” I use this evidence from the present to move slowly back into the past. New Zealand is one of the most recently settled regions on earth. To explain how the wave theory of evolution works I therefore use what we understand of the evolution and eventual mixing of the two main groups of people, Pakeha and Polynesian, in my home country.

In Part III - “Knowledge” I widen the perspective through both time and space. I show that these processes at work in New Zealand also explain all the fossil and genetic evidence for the evolution of all the various kinds of animals, birds and plants, along with the patterns of their distribution around the earth.

In Part IV - “Wandering” and Part V - “Conquest” it’s time to turn around, and start at the beginning. The jury will then be able to follow, examine and understand the meandering strands of our species’ evolution since our separation from the other apes, “The First Point”[Origin].

This will leave us with the problem of where to finish.

It will be least complicated to finish when we arrive at history. By definition history was not possible until people were able to record their version of events by writing them down (“Mythconceptions”[Oral History]). Writing seems to have begun near the eastern end of the Mediterranean Sea (“The Last Point”[The Eastern End]). Probably for that reason many political, philosophical and religious ideas through much of the world have their origin in the interaction of culture in and around that region. History begins there. In Part V the wave theory will help the defence explain the origin and perspective of these histories. For example the jury will see that the Old Testament of the Bible records such events as the Hyksos migration from Egypt and the migration of the Sea People. And many islands in the Mediterranean were, like the Pacific Islands, among the last places humans occupied. For these reasons the defence will call the Mediterranean Islands “The Last Point”.

The jury will also find that the history of the Mediterranean’s occupation will actually bring us around in a big circle. I’m confident that by the time you have completed that circle you will accept the defence’s interpretation of the evidence. No doubt various members of the prosecution will still disagree with many of these interpretations, but I’m afraid they’ll have to tell you themselves which ones they individually disagree with.

Because it has been so important in human history the defence will examine the evolution of culture at times. And technology. The distribution of various technologies and cultures reveals a great deal about human migration, expansion and evolution. This evidence will help the defence explain the wave theory. Of course the jury will realise it’s possible for a single person to spread culture, especially technology or an idea, and a genetic mutation must first arise in a single individual. But technology and many aspects of culture have always travelled faster and usually further than genes.

Although technology is really a part of culture the defence case will look at technology separately. Technology usually leaves evidence in the archaeological record whereas most other elements of culture don’t show up so well. It is also almost certain that in the very early stages of our existence technology was actually transmitted without language. Chimpanzees use basic tools for example.

The defence defines culture as being the things we have to learn that make us part of our social group. In their natural state most animals have to learn survival techniques off their older relations and in many ways this can be thought of as being culture. The study of wild chimpanzee and gorilla societies is especially interesting for this aspect of our evolution (see for example Fossey 1983, and Goodall 1990). But within the concept of culture the defence includes here only those things we learn through language: knowledge, beliefs, music, art, games, rituals, traditions, ideas, etc. (and obviously the language we speak is part of our culture). In fact the jury will see that this whole case is the result of a cultural exchange of knowledge accumulated by a huge number of humans ranging from friends and neighbours to people I have never met, including many who died long before I was born. You can probably already accept that culture evolves. In fact the defence will argue that technology and culture even obey much the same biological rules that species do. No doubt a general acceptance of the wave theory of genetic, cultural and technological evolution would ultimately lead to a change in culture.

The Prosecution

The prosecution are those of us who, perhaps to make money off others of us, maintain the defendant doesn’t exist. They constantly chant that there can be no absolute proof of Human Evolution. Of course it is very seldom evidence provides “absolute proof” of anything. It can only suggest probabilities. The defence would remind the jury that there is actually a totally overwhelming lack of proof for any theories the prosecution offers for our arrival on earth. The prosecution’s proof of their own beliefs simply involves pointing at particular ancient books. The only evidence they offer is to point at the current gaps in our knowledge. The defence suggests that the prosecution’s case relies totally on the theory of negativity: life couldn’t have evolved because it wouldn’t display the complexity it does if it hadn’t been created. Follow that?

The defence asks the jury not to be distracted into considering any other cases evolution-deniers have brought. These include “The Origin of Life” and “The Origin of the Universe”. We’ll look briefly at them in “Time” but these cases are best heard separately. And we should stick with what we can easily prove beyond reasonable doubt, Human Evolution from apes until today.

Besides, even many supporters of the modern idea of Intelligent Design, for example, would not dispute either the pattern or the time frame for Human Evolution suggested by the evidence the defence will present. They simply believe their God has had a purpose in guiding this evolution, from ape right up until today, especially during the historical events covered in “The Last Point”. A supporter of Intelligent Design (Wells 2000) concedes: “Obviously, the human species has a history. Many fossils have been found that appear to be genuine, and many of them have some features that are ape-like and some that are human-like”. The defence will offer these fossils as evidence later during the trial.

Of course even a very casual look at the evidence shows us at least some evolution has occurred, even if only a little bit. If we accept for now the widespread belief that humans descend from just one couple the only possible explanation for the variation we see in humans today is some form of evolution. A closer look at the evidence shows us that different species can actually be classified into groups that seem to be related. Members of the prosecution often explain this by claiming that various “kinds” were created, which they admit then evolved into these groups of species. But they are extraordinarily secretive as to exactly what kinds were created, and when.

The Defence

Not surprisingly the prosecution prefers drawing attention to disagreements among the defence rather than pointing at their own much more extreme differences. Members of the defence all agree that humans have a close genetic relationship with the apes of Africa: the chimpanzee and gorilla, and all three have evolved from a common ancestor. Several interpretations are possible for the evidence surrounding this common ancestor, though, and we’ll return to this when we reach “The First Point”. By then we’ll be able to use the wave theory of genetic, cultural and technological evolution to interpret the evidence.

The main disagreement within the defence concerns two conflicting theories concerning the pattern of our evolution.

We could call the first of these the “single origin” theory. This states modern humans evolved in Africa one or two hundred thousand years ago, moved out of that continent at some time and replaced all earlier human types. Genetic evidence showing all humans alive today share a male and a female ancestor supports the theory. There is also some fossil and other genetic evidence for the single origin theory. Supporters believe this is how evolution usually works; a small group expands and takes over. The theory has the advantage that it coincides, to some extent, with widely held cultural beliefs. It may even derive from them. In fact the two ancestors are often referred to as “Y-chromosome Adam” and “mtEve”.

The “spread origin” theory states humans have been what can be defined as a single species for much more than just the last 200,000 years. Our evolution has been by change and gene flow, the continuous separation and intermingling of human populations. The theory’s supporters suggest the evidence for mtEve represents something far more complicated than what has generally been promoted to the public. They believe that no species, including the human species, descends from a single individual, a single couple or even a single small group. But people always demand simple answers to complex questions.

Me

I must stress that this is my personal presentation. I’ll point out when it is specifically my interpretation but at other times I assure the jury that the interpretation offered is widely accepted by scientists such as anthropologists, zoologists, botanists, ecologists, geneticists, geologists, archaeologists, palaeontologists and linguists. Most of them would agree with most of my explanations but the jury will see that at times I offer an interpretation that scientists from one side or the other of any debate might not agree with.

People who specialise in the various sciences can perhaps become too involved in their own particular field to be able to look objectively at all the evidence. My training is in the more general field of agriculture. Agriculture requires knowledge of animal behaviour, practical animal and plant breeding and ecology, as well as an awareness of climate fluctuations, geology and an interest in nature generally. In fact farmers are trying to influence evolution every time they decide which animals to breed from and what weeds to destroy. They actually make better decisions if they are aware of this.

I have brothers who have been dairy farmers and because our parents were farmers I had the good fortune to be brought up on one. Farmers are all involved with the practical side of genetics. They usually notice that if they form a hybrid, or a cross between two different animal breeds, the individual or line of individuals they finish up with has a mix of characteristics from each original parent breed. In fact many characteristics are sort of halfway between the two. I’m confident that after examining all the evidence available you will accept that the evidence reveals at least some influence of the spread origin theory. The single origin theory requires selectively ignoring some of the evidence.

Modern developments in agriculture, especially in plant and animal breeding, provide us with a great deal of information about how this sort of evolution works. But people in the industry are often reluctant to use the information to support the defendant. It might involve them in controversy and perhaps alienate some of their clients. Many probably also lack time to find all the information.

I have been a musician for most of my life and through my interest in various types of world music, I have noticed that as the many tunes and musical styles move around the world they combine and alter, they change. In other words music evolves. Music is a part of our group’s culture and reinforces the sense of belonging to that culture. Historically the role of a musician in many societies has been to recite the genealogies, the history and the mythology of people in that society. Unfortunately I haven’t yet been able to put my story to music. However I do use several phrases many times and you may call these choruses if you wish. Of course you can choose for yourself the music you use as accompaniment while you study the evidence.

You

You will find that, like most things, the whole idea is stunningly simple to understand once you grasp it. Unfortunately, also like most things, it is difficult to explain simply otherwise it would be already totally accepted. This is not a straightforward story. Our family history is the result of diversification, amalgamation and interaction with other humans and other species (plants, diseases, animals etc.), and even changes in the earth itself. Because we can be sure the prosecution will very quickly pounce on the slightest gap in the evidence the jury will find this case at times becomes quite detailed and contains some technical terms. Fortunately it’s not necessary for you to remember the details in order to follow the story. You may even be able to follow it simply by looking at the maps, or by starting at “The Last Point”. Once you understand it you will be able to explain it to others.

The defence has tried to keep the number of “Witnesses Called” (in the form of references) to a manageable level. The reference given is the one members of the jury should easily find through a local library or on the Internet, but it is not necessarily the primary reference. If you are interested in following a particular subject up you should have no difficulty finding the primary references through the ones given.

The prosecution often claims there has been a huge conspiracy. They suggest that we, the defence, have somehow persuaded all these witnesses to make up evidence in support of the defendant. You will come to realise that the evidence many witnesses offer was not originally directly connected at all to the defendant. Most of the witnesses didn’t actually set out to provide evidence in support of the defendant in any way. In fact many may still not be aware of the significance of their evidence.

A quick word about dates. Most dates used in this case have “about” in front of them. Again the prosecution seems to have trouble with this. They expect the defence to be able to say that, for example, the Polynesians first arrived in Hawai‘i at 4.25 p.m. on the 23rd of August 432 AD. Surely “about 400 AD” is near enough. Modern dating methods such as carbon dating are always presented with a margin of error but this doesn’t mean they are therefore totally wrong and can be dismissed. Political polls also have a margin of error. It’s mainly the politicians who are shown to be losing who dismiss the polls’ general accuracy though. “About 30,000 years ago” is obviously much longer than “about 3000 years ago”. Interestingly you will find that members of the prosecution who criticise the lack of precise dates for the various stages of human development seldom provide any real evidence for accurate dates to support their own beliefs.

The Chinese Drover’s Very Clever Dog

There is one last point to make before we get this trial properly under way. We can quite easily come to the wrong conclusion; the conceptions we have accumulated encourage us to juggle the evidence to make it fit our beliefs. These beliefs are a product of how we are brought up. And we usually assume our own beliefs are superior to any others. They are the ones we know best.

We are all products of our cultural environment (Howe 2003). We are all completely unaware of what shared beliefs and personal biases we bring to our understanding of the world and how it works. Our conception of the universe is slowly built up through our lifetime, and the beliefs we form at each stage of our life as we grow up, especially those formed during early childhood, are very difficult for us to discard. In fact we can understand new information only by relating it to our pre-existing beliefs, or what the defence will later call our “Mythconceptions”. The defence suggests that widespread collective assumptions, preconceptions, and prejudices may have influenced generally accepted interpretations of the evidence concerning the defendant. Or even influenced the choice of what evidence has actually been either examined or ignored. Assumptions, preconceptions and prejudices certainly influence our individual conceptions.

My father grew up during the 1920s in the small country town of Eketahuna. There was a Chinese drover in the area. In those days (before stock trucks) people called drovers used dogs to move cattle from place to place. When my father was quite young he told my grandfather that the Chinese drover’s dog was very clever. When asked why he replied, “He understands Chinese”. Through his own assumptions, preconceptions and prejudices my father had presumed English would be a dog’s first language. It was obviously the normal language. All the people and dogs he’d had anything to do with understood it. And none of the other dogs he’d ever seen understood Chinese. The Chinese drover’s dog may well have been very clever but the fact it understood Chinese is not relevant evidence. This is an example of how what we already accept as being true prevents us from looking at the evidence objectively, or even at all of it. This affects our conclusions.

The problem is by no means confined just to children. In fact the defence will use the expression “Chinese drover’s clever dog syndrome” as one of the choruses as the trial proceeds.

No doubt many members of the prosecution will question the defence’s comparing humans with birds, animals and plants. But surely it is the prosecution who must first provide evidence to prove to the jury exactly how, why, and in what specific ways, humans differ. The defence suggests that the idea there are two sets of biological rules, one for humans and one for the rest of nature, may be our first example of Chinese drover’s clever dog syndrome, juggling the evidence to make it fit pre-existing assumptions, preconceptions and prejudices.

Most members of the jury will have heard of genes and know they are responsible for our inherited characteristics. As you probably already know, your genes control such things as your skin, hair and eye colour, the shape and size of your face, eyes and nose, your blood group and to a large extent your general height and shape as well as many other things, such as elements of your personality (Steve Jones 2000). One of my brothers believes even the willingness, or otherwise, of individual dairy cows to come into the open side of a herringbone milking shed is inherited. Anyway it is most likely that instinctive behaviour is genetically inherited in some way. Humans have many instincts. One of them is the ability to learn a language (Ridley 2000). We’ll come back to language periodically.

Humans may have up to a hundred thousand genes although the precise figure is debated. Some say many less than half this number but, almost certainly, the complex interrelationships between genes are usually underestimated. A change in a single gene can have a huge effect. For example cultivated maize differs from its vastly different wild form in just five genes (Jobling et al 2004). The environment we are brought up in does affect the influence of our genes, and some evidence indicates it may influence the genes themselves, but we can ignore both of these possibilities for now.

Experiments have shown that genes for each of your characteristics occur in pairs, one of each pair from your mother and your father. If the two genes of a pair are different usually only one of them gives rise to your observed characteristics. This one is called the “dominant” gene. The other one remains hidden but can be passed on to any of your offspring. This gene is called “recessive”. The evidence shows that your genes are carried on your chromosomes, which are confined to the nucleus (the centre) of each cell of your body. Except for the Y-chromosome, chromosomes usually occur in pairs. In fact the jury will see that a hierarchy of pairing passes on genetic information.

Y-chromosome

Each single chromosome, of each pair, consists of a double string of DNA (deoxyribonucleic acid) mixed with proteins. DNA is actually a string of what are called nucleotides attached to a series of alternating sugars and phosphoric acid (technically the nucleotide is the combination of all three chemicals). Just four types of nucleotides are present in the chain. In DNA they are adenine, thiamine, guanine and cytosine or A, T, G and C. Each strand of DNA is a string of up to a hundred million of these four nucleotides in various sequences giving a total of about three billion for the total human genome (see for example Stringer and McKie 1996). In the paired strand of nucleotides in each chromosome the adenine in one strand is always joined by hydrogen bonds to thiamine in the other, and guanine in one is joined to cytosine in the other strand (A-T, G-C). This means that chromosomes are easily able to replicate themselves. When the double strand of DNA splits each separate strand must replicate the other strand. Therefore the two new chromosomes, or double strands of DNA, are exactly the same as the original chromosome. The defence has included drawings of dividing strands of DNA in the genetic maps presented later (see for example map 2).

The main visible aspect of the function of DNA is the form we take as a developing foetus, our general shape and what type of creature we are. However in many parts of our body throughout our life DNA continually reproduces itself. This replaces our worn out tissue. But mistakes do occur and cancers can result.

In fact mistakes in the sequence of nucleotides in the DNA are reasonably common and are called mutations. Even identical twins have a few dozen differences in their total DNA (Cavalli-Sforza 1995). Harmless mutations in your reproductive cells are passed on to your descendants. These mutations lead to variation in the genetic makeup of individuals, and ultimately of different populations. In some cases it has been possible to work out the sequence in which such mutations have occurred. We’ll come back to this soon.

Apart from reproductive (sperm and egg) cells each cell of the human body has 46 chromosomes, made up of 23 pairs. Chromosome pair 23 is either a pair of X-chromosomes or a single X and a single Y chromosome. This determines whether you are female (XX) or male (XY). This is not true for all creatures. In birds and butterflies for example it is the female that has the equivalent of the XY combination.

Reproductive cells have only one of each pair of each chromosome, i.e. for humans 23 chromosomes including either a single X or a single Y. When fertilization occurs the normal condition of pairs is restored, one of each pair from each parent. Individual chromosomes are not passed unaltered from generation to generation though. Pieces can cross between the pairs of chromosomes during the formation of the reproductive cells. Because of this, genes from each parent can be thought of as mixing sort of randomly for the next generation. Gene linkages do occur, basically because genes close together on the chromosome are less likely to be separated (Jobling et al 2004). For example the genes for blond hair and blue eyes usually go together in humans, although they do show some independence.

During the formation of reproductive cells the pair of X-chromosomes in women behaves in much the same way as all the other pairs of chromosomes do, they mix. But, because there is no corresponding part on the X-chromosome for it to join with, most of the Y-chromosome is passed virtually unchanged from father to son. And virtually all genes on the single X-chromosome in men, which can come only from their mother, are expressed. This is why such things as baldness in men come through the mother’s side. Scientists have worked out the sequence of nucleotides in sections of what is called the non-recombining portion of the Y-chromosome (NRY). The differences reveal how closely related male members of different populations are. Scientists have constructed a family tree for the human Y-chromosome (“MtEve”[The Trees]). Large sections of it came from such witnesses for the defence as Hammer and Horai (1995), Karafet et al (1999), Underhill et al (2001) and Ke et al (2001). We are getting to know a great deal about migration of at least the male half of the human population. But we cannot automatically assume these movements always indicate population migrations that included women. It is not only married men who migrate to new regions. Any man who travels a lot can spread his genes, including his Y-chromosome, quite widely. For many reasons women’s genes usually spread more slowly.

Nuclear DNA

DNA is ultimately responsible (via RNA) for making proteins. Living matter is made up largely of protein. Matt Ridley (2000) writes “almost everything in the body, from hair to hormones, is either made of proteins or made by them”. Proteins are just long chains of amino acids. Twenty amino acids are commonly found in nature. Each amino acid is, in effect, coded for by a particular sequence of three nucleotides on the DNA. The pattern of nucleotides on the DNA therefore ensures a particular protein always has the same sequence of amino acids; but any mutation in the DNA can change some aspect of the protein it is responsible for and even the creature itself. It has been shown statistically most mutations seem not to have any effect though (Lewin 1999).

Any harmful protein change would usually be eliminated during foetal development, or possibly even before conception. Mutations that provide an advantage for any individual with it are probably very few and far between. Harmless protein changes move slowly through a population, as individuals with the mutation move around and leave descendants. But particular mutations are usually concentrated in particular geographical regions. The book “History and Geography of Human Genes” by Cavalli-Sforza et al (1994) can provide many hours of contemplation. It contains about 500 maps of the distribution through the world of various genetically controlled blood proteins and enzymes. Further processing of this data by a system called “principal component analysis” has provided maps of mutations that tend to occur together in clumps. The map of the first principal component for each region shows the distribution of the greatest level of genetic variation within that region.

Because, by definition, the maps pick up only genes that display regional variation the two opposite extremes are usually each concentrated in separate regions, but they merge gradually into each other. Once the regional genetic combination that makes up the first principal component is removed the next most common one (second principal component) is revealed, often showing a completely different pattern, and so on.

Studying these maps gives us an indication of the migration of different human populations around the world and the defence will call on Cavalli-Sforza’s maps many times as evidence in favour of the defendant. Of course humans, like all species, share the vast majority of their genes with each other. That is why we all look roughly the same but this case will concentrate mainly on those genes that vary within each species and group of species.

Although DNA evidence is readily accepted in Courts of Law to establish close relationships or the identity of individuals it does seem as though many of us are unwilling to accept DNA evidence of relationships in the present case. Of course the same mutation at the same point on the DNA molecule in two different individuals at different times may lead to our misinterpretation of the evidence in some cases.

So at conception you received genes from each parent in the ratio of 50:50. Some research suggests that the egg is able to select the best sperm, but the selection of genes from each parent is basically random. So when you were conceived you took half your genes from your father and half from your mother which, mixed together, make up your characteristics.

Dominant and Recessive Genes

Each of your genes provides two possibilities, one from your mother and one from your father. Any gene always expressed as a characteristic is called the dominant gene. By convention the dominant gene is written with a capital letter, e.g. “B”. The lower case letter, “b”, is used for the recessive (the one that usually doesn’t show). Because each individual has two genes for each characteristic the only possible combinations are “BB”, “Bb”, “bB” and “bb”. You can put the gene from your mother or your father first but be consistent. It sometimes makes a difference whether the gene comes from the mother or the father (Jones 2000). The reasons for this are complex and needn’t concern us. “BB” and “bb” are called “homozygous” (the same gene on each chromosome) and “Bb” and “bB” are called “heterozygous” (different gene on each chromosome).

Dominance can actually be complete or incomplete. In the case of complete dominance the first three examples above would all look the same for that characteristic. Just the one individual in four with the combination “bb” would look different. In cattle the black colour is dominant. In that case “B” could represent a dominant gene for the colour black and “b” represent a recessive gene for the colour white. The combination “bb” would be the only one that would produce a white animal. The other combinations would all be black.

A particular gene always occurs at a particular section of a chromosome. In each individual only two options are available because they have pairs of chromosomes, one of each pair from each parent. But in the population as a whole there may be many different genes available for that place. Human blood groups, for example, have three options on the chromosome: A, B and O.

Four blood groups exist: O, A, B or AB. O is recessive and so always homozygous (oo) but A and B can be homozygous (AA and BB) or heterozygous with O (Ao and Bo). AB is an example of incomplete dominance. This is what makes us all so different. And in the case of the B and b example a gene for a reddish-brown colour could be available as well as genes for black or white. This complicates things but dominance may still be complete. Black may be dominant over both red and white, and red dominant over white for example.

Some genes are co-dominant or cumulative: the heterozygous “Bb” or “bB” can be sort of halfway between the homozygous “BB” and “bb”. For the example of black and white given above the heterozygous individuals would be some shade of grey. With the addition of the red gene a combination of red and black could give a dark brown or bay colour, and red and white a fawn or dun colour. In some cases heterozygous individuals (“Bb” or “bB”) are actually at an advantage over either homozygous extreme. This is one of the things that ensure “hybrid vigour” or “heterosis”. In practice, though, characteristics that vary along a continuum between two extremes are usually the product of several different pairs of genes at different places even on different chromosomes, which individually demonstrate complete dominance.

In actual fact black is not the dominant colour in all animals. For example white is dominant in cats. In this particular case the gene that gives rise to the white also leads to deafness and white cats, especially males, are usually deaf (Jones 2000). This means there has been what is called “selection” against white cats, otherwise all cats would be white (I would bet there has also been selection against white cats for other reasons as well. Except in snow a white cat is easier to see when it is hunting or being hunted for instance).

The concept of selection has been borrowed from farming. Farmers control which individuals in their dairy herd, for example, will be able to leave more genes in the form of descendants. They do this by “selecting” which animals to either breed from or get rid of. In effect nature does much the same thing with animals and plants. If individuals with a particular characteristic are less successful at breeding those without the characteristic will make up the population numbers. This is called natural selection.

Selection keeps disadvantageous mutations at a low level. But if a dominant gene appears in a population it obviously spreads very rapidly through the generations if individuals with it leave more offspring that in turn leave more offspring etc. A recessive gene spreads more slowly because selection can operate only on individuals where the gene is expressed, i.e. those born with a double recessive. If individuals with a double recessive leave more offspring after many generations the whole population will have become double recessive. The dominant gene will then be extinct. By that time another advantageous recessive may have arisen in the population at the same point on the chromosome. In this way a recessive gene can become dominant but not, of course, over any gene it had previously been recessive to. The defence will expand on this in “Hybrid vigour and Inbreeding”[Wave Theory of Evolution].

And I’m afraid it is not really even that simple. Many animals have genes that make the two colours paler, appear in patches, stripes or spots on their bodies, and some even have three colours. Calico, or tortoiseshell, cats for example can have three colours. Most genes for colour in cats happen to be carried on the X-chromosome. To get a tortoiseshell and white cat there has to be a red gene on one X-chromosome and a black gene on the other X-chromosome as well as other genes that promote patching with white. Because males have only one X-chromosome tortoiseshell cats are usually female. Any males that are tortoiseshell-coloured must have an extra X-chromosome and they are sterile.

Genetic information therefore is carried in a way that allows an almost infinite variety of possibilities. A number of genes are available for each point on the chromosome and a number of points on the chromosome can carry similar genes. There are also genes responsible for switching on or off other genes. In fact most characteristics are almost certainly the result of a series of such genes (Ridley 2000). For any characteristic there is a sort of hierarchy of genes. Whether a gene is dominant or incompletely dominant is probably also ultimately under genetic control.

For practical purposes we can regard populations, or whole species, as being simply collections of genes, or nuclear DNA, in various proportions. The study of this is called population genetics and the defence will use information gained from studying cattle to explain the idea many times during this case. Because a great deal of information is available for cattle they are ideal for the study of practical genetics. Not only have desirable qualities been bred for; the change each generation can actually be measured.

Meat quality, weight and growth rates for beef cattle progeny can be measured accurately. In dairy cows milk production, protein and fat percentage in the milk, overall size, temperament, teat placement and udder shape are all to some extent genetically controlled and can be measured, or at least subjectively judged. All these individual traits have what is called a bell curve distribution. As you move away from the most common type in any direction numbers fall off in the shape of a bell. The further from the majority you get the fewer individuals there are. The jury will eventually understand how we can see that in effect each individual gene travels through a population on its own independent wave.

My grandfather milked Shorthorn and Red Devon cattle breeds. By the time my uncles took over the farm Jersey cattle had become the fashion. But they didn’t need to buy a whole new herd. They just formed a sequence of hybrids with Jersey bulls. After three cow generations the herd was ⅞ Jersey (“Pedigrees”[Ancestry]). They looked like Jerseys but when I was a child some cattle in the herd still had pink noses or were brindled, a throwback to the earlier breeds. Their fathers had Shorthorn or Red Devon ancestry too.

When Friesian cattle then became popular it was again possible to gain a Friesian herd by the same method. But the mitochondrial DNA of many Friesian cows in the New Zealand dairy herd goes right back to Shorthorn or Red Devon cattle.

Mitochondrial DNA

So far we have been dealing with nuclear DNA, the DNA responsible for your genes. But there is another type of DNA in your body. It is called mitochondrial DNA (mtDNA). This DNA is not involved with the formation of genes (Jones 2001) and it occurs as a circular molecule (the ends are connected). Human mitochondria each consist of just sixteen and a half thousand pairs of the nucleotides: A, T, G and C. Each cell of the human body may have up to ten thousand molecules of mtDNA but most have far fewer. Mitochondria occur outside the nucleus and are known as the powerhouse of the cell.

They produce the proteins responsible for digestion within the cell. These proteins are involved in the production of ATP (adenosinetriphosphate) from various acids produced in the body. This process takes up oxygen and produces carbon dioxide and water. In the vast majority of individuals all the mitochondria in every cell have exactly the same DNA but mutations do occur. If the mutation happens in an egg cell it is passed on to the offspring.

The egg cell needs its mitochondria for metabolism and cell division but the sperm’s mtDNA is effectively discarded and lost at fertilization (Jobling et al 2004). Therefore the mtDNA is passed unchanged from only the mother to the child for thousands of generations. In fact the mtDNA does change over time (mutations). The rate of this change and the regularity of the change have been greatly debated by scientists; i.e. does it have a sort of half-life? How much does it change, say, in a thousand years? Is the change totally random or does selection act on these changes? It is now generally accepted that some sections of mtDNA change quite rapidly and regularly, and it has been shown that one parent-child comparison in forty has a mitochondrial mutation (Jones 2000). Because there is a great deal of mtDNA in each individual, and it is a relatively short chain, it has been the easiest DNA to extract and to study.

Like the Y-chromosome, the sequence of the nucleotides in sections of the mtDNA has been worked out for individuals of many species. The accumulation of differences in the sequences can be used to indicate the relationship of various groups of animals and humans through their mother’s ancestry. If the mtDNA is only a little different it is presumed they are closely related and of course this would be so, no matter what the rate of mutation.

Again, like the Y-chromosome, examination of the mutations in human mtDNA has been used to construct an evolutionary, or family, tree. From this it has been concluded we all descend from a single woman who lived in Africa. We will meet her again and see her family tree in “MtEve”[The Trees]. But before then the defence needs to explain a few more things.

Studies of the changes in mitochondrial DNA and the Y-chromosome have been very useful in helping us understand our origin but we need to consider other evidence before we jump to conclusions. The first thing we need to consider, and explain, is the present distribution of human genetic variations.